Copolymer, composition and method for modifying rheology

ABSTRACT

A copolymer for modifying rheology is formed of monomer units consisting essentially of at least one first monomer unit comprising a polyhedral oligomeric silsesquioxane having an ethylenically unsaturated radical; at least one second monomer unit comprising an unsaturated oligo-poly(dimethyl siloxane)(meth)acrylate; and a sufficient amount of at least one unsaturated water-soluble monomer, such that the copolymer is soluble in water. A composition may comprise an electrolyte and the copolymer. The rheology of an environment comprising an electrolyte may be modified by adding the copolymer to the environment.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a U.S. National Phase Application under 35U.S.C. §371 of International Application No. PCT/SG2011/000445, filedDec. 21, 2011, entitled COPOLYMER, COMPOSITION AND METHOD FOR MODIFYINGRHEOLOGY, which claims the benefit of, and priority from, United StatesProvisional Patent application Ser. No. 61/425,497, filed Dec. 21, 2010,and entitled “Copolymers as Rheology Modifiers,” the entire contents ofwhich were incorporated by reference.

FIELD OF THE INVENTION

The present invention relates generally to rheology modifiers, andparticularly to rheology modifying copolymers and related compositionsand methods.

BACKGROUND OF THE INVENTION

A rheology modifier (RM) can be used to increase the viscosity of acomposition containing the RM. Conventional rheology modifyingcompositions that allow modification of viscosity ofelectrolyte-containing environments include cross-linked linearpoly(vinyl amide/unsaturated carboxylic acid) copolymers, andcross-linked copolymers formed of unsaturated carboxylic acid, ahydrophobic mercaptan monomer, a thioester or amino acid containingchain transfer agent into the copolymer composition, and a cross-linkingagent. For example, hydrophobically modified hydroxyethyl cellulose orethylhydroxyethyl cellulose, hydrophobically modified ethoxylateurethanes, and hydrophobically modified alkali-soluble or swellableemulsions are known to modify rheology.

SUMMARY OF THE INVENTION

According to one aspect of the invention, there is provided a copolymerfor modifying rheology, formed of monomer units consisting essentiallyof at least one first monomer unit comprising a polyhedral oligomericsilsesquioxane having an ethylenically unsaturated radical; at least onesecond monomer unit comprising an unsaturated oligo-poly(dimethylsiloxane)(meth)acrylate; and a sufficient amount of at least oneunsaturated water-soluble monomer, such that the copolymer is soluble inwater.

In some embodiments, the copolymer may comprise about 1 to about 30 wt %of the at least one first monomer unit, about 1 to about 40 wt % of theat least one second monomer unit, and about 30 to about 98 wt % of theat least one unsaturated water-soluble monomer, based on the totalweight of the monomer units and the at least one unsaturatedwater-soluble monomer.

In some embodiments, the copolymer may comprise about 5 to about 8 wt %of the at least one first monomer unit, about 4 to about 35 wt % of theat least one second monomer unit, and about 60 to about 90 wt % of theat least one unsaturated water-soluble monomer, based on the totalweight of the monomer units and the at least one unsaturatedwater-soluble monomer.

The at least one first monomer unit may comprise a monomer unit offormula (I):

wherein Y is independently an ethylenically unsaturated radical, forexample, acryloxypropyl; and each R is independently a C₁-C₁₂ monovalenthydrocarbon radical such as i-butyl, a C₁-C₁₂ monovalent hydrocarbonradical comprising an ether linkage, a halogen-substituted C₁-C₁₂monovalent hydrocarbon radical, or a halogen-substituted C₁-C₁₂monovalent hydrocarbon radical comprising an ether linkage.

The at least one first monomer unit may also comprise a monomer unit offormula (II), (III) or (IV):

wherein each R is independently a C₁-C₁₂ monovalent hydrocarbon radical,a C₁-C₁₂ monovalent hydrocarbon radical comprising an ether linkage, ahalogen-substituted C₁-C₁₂ monovalent hydrocarbon radical, or ahalogen-substituted C₁-C₁₂ monovalent hydrocarbon radical comprising anether linkage. In some embodiments, the R may each be i-butyl in formula(II), (III) or (IV).

The copolymer may comprise 5 repeating units of the at least one firstmonomer unit.

The at least one second monomer unit may comprise a monomer unit offormula (V):

wherein X is an activated unsaturated radical, for example,(meth)acryloxy; R¹ is a C₁-C₂₂ divalent hydrocarbon radical, forexample, propylene; R² is a C₁-C₂₂ monovalent hydrocarbon radical, forexample, n-butyl; each R³ is methyl; and y is from 1 to 200.

The copolymer may comprise 1 to 5 repeating units of the at least secondmonomer unit.

The at least one unsaturated water-soluble monomer comprises a monomerhaving the formula (VI):

wherein m is an integer from 0 to 10; A is a methylene group; R⁴ is ahydrogen atom, a phenyl group, or a benzyl group; R⁵ is a hydrogen atom,or a lower alkyl or carboxyl group; R⁶ is a hydrogen atom, a lower alkylgroup, —CH₂COOH, a phenyl group, a benzyl group, or a polymeric groupcomprising a unit derived from a sulfonic acid; and Z is COOH,COO(B)_(n)Y¹, or CON(R⁷)R⁸, wherein R⁷ and R⁸ is each independentlyhydrogen or (B)_(n)Y¹; B is a methylene group; n is an integer from 1 to10; and Y¹ is a hydroxyl group, primary amine, tertiary amine, orquaternary ammonium salt.

The at least one unsaturated water-soluble monomer may comprise acarboxylic acid such as an acrylic acid.

The copolymer may be a random copolymer, a block copolymer or a graftcopolymer.

According to another aspect of the invention, there is provided acomposition comprising an electrolyte and the copolymer describedherein.

According to another aspect of the invention, there is provided a methodof modifying the rheology of an environment comprising an electrolyte,the method comprising adding the copolymer to the environment. Theenvironment may comprise a solution and the copolymer is added to thesolution.

Other aspects and features of the present invention will become apparentto those of ordinary skill in the art upon review of the followingdescription of specific embodiments of the invention in conjunction withthe accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

In the figures, which illustrate, by way of example only, embodiments ofthe present invention,

FIGS. 1A, 1B, 1C and 1D are schematic diagrams showing possible chemicalstructures of a first component of a rheology modifying copolymer,according to embodiments of the present invention;

FIG. 2 is a schematic diagram illustrating a synthesis route for forminga polyhedral oligomeric silsesquioxane (POSS) monomer;

FIG. 3 is a schematic diagram showing the chemical structure of a secondcomponent of the copolymer;

FIG. 4 is a schematic diagram showing the chemical structure of a thirdcomponent of the copolymer;

FIG. 5 is a schematic diagram showing the chemical structure of acopolymer, according to an embodiment of the present invention;

FIG. 6 is a schematic diagram illustrating a synthesis route for formingthe copolymer of FIG. 5;

FIG. 7 is a ¹H-NMR spectrum of a sample copolymer; and

FIG. 8 is a ¹H-NMR spectrum of a sample POSS monomer.

DETAILED DESCRIPTION

In overview, it has been recognized that a rheology modifier can beformed from a copolymer consisting essentially of (a) a monomer unitcomprising a polyhedral oligomeric silsesquioxane (POSS) having anethylenically unsaturated radical; (b) a monomer unit comprising anunsaturated oligo-poly(dimethyl siloxane)(meth)acrylate (PDMS-MA); and(c) a sufficient amount of an unsaturated water-soluble monomer, wherethe copolymer is soluble in water. In a specific embodiment, thewater-soluble monomer may be an acrylic acid.

The numbers of (a) and (b) monomer units in the copolymer may vary. Insome cases, the copolymer may include about 1 to about 99 wt % of theunsaturated water-soluble monomer, about 1 to about 99 wt % of thePOSS-bearing monomer, about 1 to about 99% of the PDMS-MA monomer, basedon the total weight of these monomers.

In a selected embodiment, the copolymer may contain about 30 to about 98wt % of the unsaturated water-soluble monomer, about 1 to about 30 wt %of the POSS-bearing monomer, and about 1 to about 40 wt % of the PDMS-MAmonomer. For example, the copolymer may contain about 5 to about 8 wt %of POSS monomer units, about 4 to about 35 wt % of PDMS-MA monomerunits, and about 60 to about 90 wt % of unsaturated water-solublemonomers, based on the total weight of the monomer units and theunsaturated water-soluble monomer.

Conveniently, such a copolymer may be combined with an electrolyte in acomposition to form a rheology modifying composition, or added to anenvironment containing an electrolyte, to modify the rheology of theenvironment. The environment may be a solution such as an aqueoussolution, or an ionic liquid. The copolymer may be added to increase theviscosity of the solution.

The copolymer may be a random copolymer, a block copolymer or a graftcopolymer. The copolymer may be amphiphilic.

An embodiment is thus related to a composition containing the copolymerand an electrolyte.

Another embodiment relates to a method of modifying an environmentcontaining an electrolyte. In this method, the copolymer is added to theenvironment as a rheology modifier. The environment may be a solutionand the copolymer may be added to the solution.

The present inventors have found that a copolymer consisting essentiallyof components (a), (b) and (c) as described herein can be effective foruse as a rheology modifier in an aqueous environment without anyadditional copolymer component.

Component (a)—POSS monomer(s)

A polyhedral oligomeric silsesquioxane (POSS) has a three-dimensionalmolecular structure in which at least two siloxane rings are connectedto form a relatively rigid structure (referred to as a cage structureherein). Suitable POSS-bearing monomers include those that contain atleast one substituent group comprising a polymerizable activatedunsaturated group.

Example structures of suitable POSS monomers are illustrated in FIGS.1A, 1B, 1C and 1D.

In selected embodiments, the general structure of a suitablesilsesquioxane-based monomeric unit may have the cage structureindicated as Formula (I) in FIG. 1A. In Formula (I), Y is anethylenically unsaturated radical. Each R may be independently a C₁-C₁₂monovalent hydrocarbon radical, which may contain ether linkages, may behalogen-substituted, or may be halogen-substituted and contain etherlinkages.

A suitable POSS monomer should contain at least one polymerizable site.An ethylenically unsaturated group conveniently provides a polymerizablesite. An ethylenically unsaturated radical is an unsaturated group thatincludes a substituent for facilitating free radical polymerization,such as a vinyl-containing substituent.

Example suitable Y radicals include (meth)acryloxy, (meth)acrylamido andstyryl. As used herein, the term “(meth)” denotes optional methylsubstituent. The (meth)acryloxy, (meth)acrylamido and styryl radicalsmay be substituted with an alkyl group. A (meth)acryloxy radical, forexample, acryloxypropyl, may be advantageous over other radicals in someembodiments.

Example R radicals include alkyl, cycloalkyl, aryl, aralkyl, alkary,alkoxyalkyl radicals, and their halogen-substituted derivatives. In someembodiments, a C₁-C₄ alkyl, such as isobutyl, may be used.

The POSS monomer in Formula (I) may have a closed-cage structure, or anopen-cage structure.

Suitable POSS monomers may have different cage sizes, either larger orsmaller than the size of the structure in Formula (I).

Suitable POSS monomers may also have structures as illustrated byFormulae (II), (III), and (IV) in FIGS. 1B, 1C and 1D. Each R in thesestructures may be independently a C₁-C₁₂ monovalent hydrocarbon radical,which may contain ether linkages, may be halogen-substituted, or may behalogen-substituted and contain ether linkages. For example, each R maybe i-butyl.

As can be understood, the structures of Formulae (II) and (III) areexamples of closed-cage structures. In a “closed-cage”, each ringsilicon atom is linked to three other adjacent ring silicon atomsthrough respective oxygen atoms.

In some embodiments, the POSS monomer may have the structure of Formula(III).

The structures of Formula (IV) are examples of open-cage structures. Inan “open-cage” structure, two or more ring silicon atoms are each linkedto less than three other ring silicon atoms through oxygen atoms. Inother words, each of these two or more ring silicon atoms is linked to agroup that is not an oxygen bonded to an adjacent ring silicon atom.

The POSS monomers can be produced by a suitable technique known to thoseskilled in the art. Example techniques are described in U.S. Pat. Nos.5,412,053, 5,484,867, 5,589,562, and 6,586,548.

In a selected embodiment, the POSS monomer may be formed according tothe synthesis route illustrated in FIG. 2, and have the chemicalstructure shown on the right hand side of FIG. 2. The R radical can bei-butyl. The yield of this process can be greater than 90%.

Component (b)—PDMS-MA monomer(s)

As used herein, a PDMS-MA monomer denotes amono(meth)acryloxyalkyl-terminated poly(dimethylsiloxane). Amono(meth)acryloxypropyl-terminated poly(dimethylsiloxane) may beadvantageously used in some embodiments.

The PDMS-MA monomer may have the Formula (V) shown in FIG. 3.

In Formula (V), X may be an activated unsaturated radical. R¹ may be aC₁-C₂₂ divalent hydrocarbon radical. R² may be a C₁-C₂₂ monovalenthydrocarbon radical. Each side group R³ may be a methyl radical. Thenumber y in Formula (V) may be an average number in the range from 1 to200.

For clarity, it should be understood that in chemical formulae orexpressions, the superscripts in expressions such as “R¹” to “R¹¹” areposition indices, and the subscripts in expressions such as “C₁” to“C₁₂” indicate the numbers of repeated atoms, units, or groups.

Suitable PDMS-MA monomer units may include polysiloxanesend-capped/terminated with polymerizable unsaturated groups, and may bepoly(organosiloxane) and polyparaffinsiloxane monomers.

Suitable oligo-siloxane monomers can be produced by a suitable techniqueknown to those skilled in the art. For example, some oligo-siloxanemonomers can be produced according to the techniques disclosed in U.S.Pat. No. 3,808,178, 4,153,641, 4,254,248, 4,277,595, and 6,545,114.

Suitable PDMS-MA monomers are also available from commercial sourcessuch as SIGMA-ALDRICH™.

An activated unsaturated radical is an unsaturated group that includes asubstituent for facilitating free radical polymerization, such as avinyl-containing substituent. Suitable X radicals include(meth)acryloxy, (meth)acrylamido, and styryl. A (meth)acryloxy radicalmay be advantageously used as X in some embodiments.

Suitable R¹ radicals include alkylene radicals. For example, suitable R¹radicals may include methylene, propylene, and butylene. In someembodiments, R¹ can be propylene.

Suitable R² radicals include alkyl radicals. For example, suitable R²radicals may include methyl, propyl, and butyl. In some embodiments, R²can be n-butyl.

Each R³ radical may be methyl.

Component (c)—Unsaturated water-soluble monomers

A “water-soluble” monomer refers to a monomer that has a watersolubility of about one wt % or greater. That is, at least about 1 g ofthe monomer can dissolve in 100 g of water. In another embodiment of thepresent invention, the water solubility of the monomer is at least about10 g in 100 g of water, and in yet another embodiment, the watersolubility is at least about 50 g in 100 g of water.

In one embodiment, the unsaturated water-soluble monomer may be acarboxylic acid, such as an acrylic acid. In other embodiments, theunsaturated water-soluble monomer may have the general structurerepresented by Formula (VI) in FIG. 4. In Formula (VI), m is an integerfrom 0 to 10. “A” is a methylene group, which may be optionally bondedto a carbon atom of an unsaturated group, or to a neighboring methylenegroup when m is greater than 1. The bonding may be through a non-carbonatom such as oxygen or sulfur. R⁴ may be a hydrogen atom, a phenylgroup, or a benzyl group. R⁵ may be a hydrogen atom, or a lower alkyl orcarboxyl group. R⁶ may be a hydrogen atom, a lower alkyl group,—CH₂COOH, a phenyl group, or a benzyl group. R⁶ may also be a polymercontaining units derived from a sulfonic acid, such as vinylsulfonic,styrenesulfonic, or acrylamidoalkylsulfonic units.

In Formula (VI), Z may be COOH, COO(B)_(n)Y¹, or CON(R⁷) R⁸. R⁷ and R⁸are each independently hydrogen or (B)_(n)Y¹. B is a methylene group,and may be optionally bonded to a carbon atom of an unsaturated group orto a neighboring methylene group when n is greater than 1, through anon-carbon atom such as oxygen or sulfur. The number n is an integerfrom 1 to 10. Y¹ is a hydroxyl (OH) group, primary amine (NH₂),secondary amine (NHR⁹), tertiary amine (R⁹NR¹⁰), or quaternary ammoniumsalt (R⁹N⁺(R¹⁰)R¹¹D⁻). R⁹, R¹⁰ and R¹¹, which may be identical ordifferent, are each independently a linear or branched alkyl grouphaving from 1 to 22 carbon atoms, such as 4 to 20 or 6 to 18 carbonatoms. The linear or branched alkyl group may be optionally interruptedby at least one non-carbon atom such as O, N, S or P. The alkyl groupmay be optionally substituted by at least one substituent, which may bea hydroxyl group or a halogen atom (CI, Br, I or F).

D⁻ is an anion, which may be a halide ion and D may be a halogen, suchas CI, Br, F, or I. D⁻ may also be a sulfate, sulfonate, phosphonate,hydroxide, borate, cyanide, carbonate, thiocyanate, thiosulfate,isocyanate, sulfite, bisulfate, nitrate, oxalate, silicate, sulfide,cyanate, acetate, or another inorganic or organic anion.

The unsaturated water-soluble monomer may be an acid monomer, such as(meth)acrylic, crotonic, itaconic, maleic, and fumaric acid monomer orthe like.

The unsaturated water-soluble monomer may also be an amino-substituted(meth)acrylamide, such as dimethylaminopropyl(meth)acrylamide,dimethylaminoethyl(meth)acrylamide,N,N-bis(dimethylaminoethyl)(meth)acrylamide, orN,N-bis(dimethyl-aminopropyl)(meth)acrylamide.

The unsaturated water-soluble monomer may also be an amino-substituted(meth)acrylate, such as dimethylaminoethyl(meth)acrylate ordimethylaminopropyl(meth)acrylate.

The unsaturated water-soluble monomer may also be ahydroxyalkyl(meth)acrylate, such as hydroxyethyl(meth)acrylate orhydroxypropyl(meth)acrylate.

Mixtures of different unsaturated water-soluble monomers may be includedin the copolymer or the mixture for forming the copolymer.

Suitable unsaturated water-soluble monomers such as acrylic acids areavailable from commercial sources such as SIGMA-ALDRICH™.

Some Possible Configurations and Synthesis Methods of Rheology ModifyingCopolymers

A rheology modifying copolymer as described above may have a molecularweight in the range of about 100 to about 5,000 K.

In a selected embodiment, a rheology modifying copolymer may have thechemical structure illustrated in FIG. 5, where R is i-butyl. Asdepicted, the number of repeating POSS monomer units is 5. In FIG. 5,m+n+o=750, which is the total number of acrylic acid monomer units. Thevalues of m, n, and o may be random and does not need to be controlled,such that the copolymer is a random copolymer. The number averagedmolecular weight (Mn) of the PDMS-MA monomers is about 4590, x is from 1to 5, y is from 1 to 200, and the ratio of the weight of PDMS-MA to thetotal weight is about 7.25 to about 28.1 wt %.

In selected embodiments, a rheology modifying copolymer may be formed bypolymerizing a mixture containing at least one monomer comprising a POSScompound including an ethylenically unsaturated radical; at least oneethylenically unsaturated oligo-siloxane monomer; and at least oneunsaturated water-soluble monomer. In selected embodiments, the mixtureto be polymerized for forming the copolymer may contain about 1 to about30 wt % of the POSS monomer, about 1 to about 40 wt % of theoligo-siloxane monomer, and about 30 to about 98 wt % of the unsaturatedwater-soluble monomer, and about 0.2 to about 2 wt % of a free radicalinitiator, based on the total weight of the monomers.

The polymerization of the copolymer may be carried out in inert diluentssuch as organic fluids or mixtures of organic fluids. Suitable solventsinclude alcohols such as methanol, ethanol and 2-propanol; ethers suchas diethyl ether, tetrahydrofuran (THF) and 1,4-dioxane; liquidhydrocarbons such as hexane and heptane; cycloalkanes such ascyclohexane; aromatics such as benzene and alkyl-substituted benzenessuch as toluene and xylene; alkyl carboxylates such as ethyl acetate,isopropyl acetate, propyl acetate, methyl acetate or butyl acetate;haloalkanes such as chloro or fluoroalkanes such as methylene chloride,ethylene dichloride and chloroform, and mixtures thereof.

The copolymer may be formed in mixed solvents, e.g. THF and methanol, ordioxane and methanol, or THF and ethanol, which can be removed after thepolymerization. The polymerization reactions may be initiated in thepresence of a free radical initiator at a polymerization temperature of20 to 100° C., such as 40 to 80° C.

Free radical initiators include persulfates such as sodium, potassium orammonium persulfates, peroxygen compounds such as caprylyl peroxide,benzoyl peroxide, hydrogen peroxide, pelargonyl peroxide, cumenehydroperoxides, diisopropyl peroxydicarbonate, tertiary butyldiperphthalate, tertiary butyl perbenzoate, sodium peracetate,di-(2-ethylhexyl)peroxy dicarbonate, azo catalysts such asazobis(isobutyronitrile) and 4,4′-azobis(4-cyanovaleric acid), and thelike.

As a general procedure for carrying out the polymerization reaction, agiven mixture was placed in a round flask, and the flask wasdeoxygenated and sealed. The mixture was polymerized by heating it in awater bath at 50° C. for 1 day. The heated sample mixture was thenplaced into an excessive amount of diethyl ether to precipitate forpurification. The precipitates were collected and dried in a vacuum ovento yield white powders.

In a selected embodiment, a rheology modifying copolymer, such as thecopolymers shown in FIG. 5, may be formed according to the synthesisroute illustrated in FIG. 6. The yield of this process can be greaterthan 95%.

As illustrated in FIG. 6, the product of polymerization is a linearcopolymer consisting essentially of acryloxy propyl isobutyl-POSSmonomers, PDMS-MA monomers, and acrylic acid monomers, and may be in theform of a white powder.

In a process for forming the copolymer, a solution for polymerizationmay be provided, which contains about 5 to about 50 wt %, such as about10 to about 25 wt %, of the mixture described above; about 50 to about95 wt %, such as about 75 to 90 wt %, of a removable organic solvent;and about 0.1 to about 5 wt %, such as about 0.2 to 2 wt %, of a freeradical initiator, based on total weight of the monomers.

Possible components and their respective percentages in the polymersolution are also listed in Table I. The listed concentrations are basedon total weight of the monomers, except in the last row which shows theweight percentage of the solvent based on the total weight of thesolvent and the monomers.

TABLE I Contents of polymerization solution Concentration ComponentsSpecific Examples (wt %) unsaturated (meth)acrylic acid,dimethyl-aminoethyl 1-99, e.g. water-soluble (meth)acrylamide,dimethylaminoethyl 30-98 monomer (meth)acrylate, hydroxyethyl(meth)acrylate POSS-bearing (meth)acryloxy propyl ethyl-(isobutyl- 1-99,e.g. 1-30 monomer or cyclopentyl-) POSS Oligo-siloxaneoligo-poly(dimethyl siloxanes) 1-99, e.g. 1-40 monomer (meth)acrylateFree radical 4,4′-Azobis(4-cyanovaleric acid), 2,2′- 0.1-5, e.g.initiator, e.g. azobis(2-methylbutanenitrile), t- 0.2-2 peroxide,butylperoxy pivalate perester Organic solvent Methanol, ethanol,2-propanol, THF, 95-50, e.g. or mixed 1,4-dioxane, chloroform, methylene90-75 solvents chloride

Conveniently, the copolymers described herein can be produced in afacile process that can be easily scaled-up. The components of thecopolymer can provide combined effects such that the copolymer can beincorporated into a product to modify the rheology of the final product,even when the concentration of the copolymer in the final product isrelatively low. In particular, the combination of POSS and PMDS-MA(unsaturated oligo-poly(dimethyl siloxane)(meth)acrylate) is shown toprovide a synergistic rheology modifying effect. The inclusion of asufficient amount of the water-soluble monomer conveniently allows thecopolymer to be used in an aqueous environment or to be incorporatedinto a product that is to be used in an aqueous environment such as inliquids that contain water.

Possible Applications of Rheology Modifying Copolymers

Without being limited to any particular theory, it is expected that therheology modifying effect of the copolymers may result at least in partfrom the mechanism discussed herein. POSS portions in the copolymer areexpected to interact with hydrophobic domains of a surfactant in asolution, resulting in increased rheology. Within a limit, a higher POSScontent is expected to provide a higher viscosity as more POSS portionscan enter and interact with the hydrophobic domains. However, when thePOSS content is higher than the limit, the copolymer molecules will tendto aggregate among themselves due to interaction between the POSSportions. As a result, less POSS portions will react with thehydrophobic domains of the surfactant, and the rheology modifying effectmay be expected to decrease, instead of increase.

The copolymers described herein may have application in personal care,home care, and pharmaceutical applications. Examples of pharmaceuticalapplications include topical formulations in the form of creams,lotions, ointments, or gels, where the copolymers may be used as awetting aid for the pharmaceutically active materials, or as a skinpenetration enhancer, or as an emulsifier for a solvent phase having anaesthetic effect, or may be present to enhance the solubility orbioavailability of the pharmaceutically active material, or may be usedas a bioadhesive agent for mucus membranes.

Embodiments of the present invention are further illustrated with thefollowing examples, which are not intended to be limiting.

EXAMPLES

In these examples, various sample copolymers were polymerized fromdifferent monomeric mixtures whose contents are listed in Table II. Thevalues given are the weight percentages of the respective componentsbased on the total weight of the mixture except the solvent.

TABLE II Viscosity (1% sample in POSS- PDMS- Solvent T Time 12% SDS)Sample AA A MA ACVA (1/1) (° C.) (day) (cps) 1 88.4 7.6 3.8 0.2 THF/MeOH50 1 14.1 2 76.9 6.6 16.3 0.2 THF/MeOH 50 1 15.0 3 59.4 5.1 35.3 0.2THF/MeOH 50 1 15.3 4 — — — — — — — 1.45

In Table II and the description below, AA=acrylic acid; POSS-A=acryloxypropyl isobutyl-POSS; PDMS-MA=oligo-poly(dimethyl siloxanes)methacrylate(M_(n)=4587); ACVA=4,4′-azobis(4-cyanovaleric acid); and SDS=sodiumn-dodecyl sulfate. Sample 4 was a control sample used for viscositytesting at 12% SDS solution.

Example 1

2 g of AA, 172 mg of POSS-A, 85 mg of PDMS-MA and 5.2 mg of ACVA weredissolved by 5 mL of THF and 5 mL MeOH mixed solvent in a 50 mL roundflask. The contents in the flask were deoxygenated by argon bubbling forhalf an hour and sealed. The mixture in the flask was stirred at 50° C.for one day, and the heated mixture was precipitated into 300 mL ofether. The white powder (Sample 1) was collected by ultrafiltration anddried at 50° C. under vacuum for two days.

Example 2

2 g of AA, 172 mg of POSS-A, 424 mg of PDMS-MA and 5.2 mg of ACVA weredissolved by 5 mL THF and 5 mL MeOH mixed solvent in a 50 mL roundflask. The contents in the flask were deoxygenated by argon bubbling forhalf an hour and sealed. The mixture in the flask was stirred at 50° C.for one day, and the heated mixture was precipitated into 300 mL ofether. The white powder (Sample 2) was collected by ultrafiltration anddried at 50° C. under vacuum for two days.

A measured ¹H-NMR spectrum of Sample 2 and the chemical structure ofcopolymer in Sample 2 are shown in FIG. 7.

In comparison, the ¹H-NMR spectrum of a POSS-A monomer is shown in FIG.8.

Example 3

2 g of AA, 172 mg of POSS-A, 1.188g of PDMS-MA and 5.2 mg of ACVA weredissolved by 5 mL THF and 5 mL MeOH mixed solvent in a 50 mL roundflask. The contents in the flask were deoxygenated by argon bubbling forhalf an hour and sealed. The mixture in the flask was stirred at 50° C.for one day, and the heated mixture was precipitated into 300 mL ofether. The white powder (Sample 3) was collected by ultrafiltration anddried at 50° C. under vacuum for two days.

Example 4

A 1% stock dispersion of Sample 1, 2 or 3 (1 g) was prepared in 12%sodium n-dodecyl sulfate (SDS) solution (99 g). In each case, themixture was stirred at room temperature for over 3 days to form ahomogeneous solution.

The viscosity of the dispersion was then measured using a RheometerRheostress 600 (THERMO HAAKE™) at 20 rpm. The measured results aresummarized in Table II and the viscosity values were determined to bearound 15 cps for all three Samples 1, 2, and 3. In comparison, theviscosity of 12% SDS solution without adding the copolymer (Sample 4)was found to be about 1.45 cps. With adding 1 wt % of the samplecopolymer, the viscosity of the final solution was enhanced to be aboutten times higher than the original surfactant solution.

It will be understood that any singular form is intended to includeplurals herein. For example, the word “a”, “an” or “the” is intended tomean “one or more” or “at least one.” Plural forms may also include asingular form unless the context clearly indicates otherwise.

It will be further understood that the term “comprise”, including anyvariation thereof, is intended to be open-ended and means “include, butnot limited to,” unless otherwise specifically indicated to thecontrary.

When a list of items is given herein with an “or” before the last item,any one of the listed items or any suitable combination of two or moreof the listed items may be selected and used. For any list of possibleelements or features provided in this specification, any sub-listfalling within the given list is also intended.

Similarly, any range of values given herein is intended to specificallyinclude any intermediate value or sub-range within the given range, andall such intermediate values and sub-ranges are individually andspecifically disclosed.

Of course, the above described embodiments are intended to beillustrative only and in no way limiting. The described embodiments aresusceptible to many modifications of form, arrangement of parts, detailsand order of operation. The invention, rather, is intended to encompassall such modification within its scope, as defined by the claims.

What is claimed is:
 1. A copolymer for modifying rheology, formed ofmonomer units consisting essentially of: at least one first monomer unitcomprising a polyhedral oligomeric silsesquioxane having anethylenically unsaturated radical; at least one second monomer unitcomprising an unsaturated oligo-poly(dimethyl siloxane)(meth)acrylate;and a sufficient amount of at least one unsaturated water-solublemonomer, such that said copolymer is soluble in water.
 2. The copolymerof claim 1, comprising: about 1 to about 30 wt % of said at least onefirst monomer unit; about 1 to about 40 wt % of said at least one secondmonomer unit; and about 30 to about 98 wt % of said at least oneunsaturated water-soluble monomer, based on the total weight of saidmonomer units and said at least one unsaturated water-soluble monomer.3. The copolymer of claim 1, comprising: about 5 to about 8 wt % of saidat least one first monomer unit; about 4 to about 35 wt % of said atleast one second monomer unit; and about 60 to about 90 wt % of said atleast one unsaturated water-soluble monomer, based on the total weightof said monomer units and said at least one unsaturated water-solublemonomer.
 4. The copolymer of claim 1, wherein said at least one firstmonomer unit comprises a monomer unit of formula (I):

wherein Y is independently an ethylenically unsaturated radical; andeach R is independently a C₁-C₁₂ monovalent hydrocarbon radical, aC₁-C₁₂ monovalent hydrocarbon radical comprising an ether linkage, ahalogen-substituted C₁-C₁₂ monovalent hydrocarbon radical, or ahalogen-substituted C₁-C₁₂ monovalent hydrocarbon radical comprising anether linkage.
 5. The copolymer of claim 4, wherein Y is acryloxypropyl,and each R is i-butyl.
 6. The copolymer of claim 1, wherein said atleast one first monomer unit comprises a monomer unit of formula (II),(III), or (IV):

wherein each R is independently a C₁-C₁₂ monovalent hydrocarbon radical,a C₁-C₁₂ monovalent hydrocarbon radical comprising an ether linkage, ahalogen-substituted C₁-C₁₂ monovalent hydrocarbon radical, or ahalogen-substituted C₁-C₁₂ monovalent hydrocarbon radical comprising anether linkage.
 7. The copolymer of claim 6, wherein each R is i-butyl.8. The copolymer of claim 1, comprising 5 repeating units of said atleast one first monomer unit.
 9. The copolymer of claim 1, wherein saidat least one second monomer unit comprises a monomer unit of formula(V):

wherein X is an activated unsaturated radical; R¹ is a C₁-C₂₂ divalenthydrocarbon radical; R² is a C₁-C₂₂ monovalent hydrocarbon radical; eachR³ is methyl; and y is from 1 to
 200. 10. The copolymer of claim 9,wherein X is (meth)acryloxy, R¹ is propylene, and R² is n-butyl.
 11. Thecopolymer of claim 1, comprising 1 to 5 repeating units of said at leastone second monomer unit.
 12. The copolymer of claim 1, wherein said atleast one unsaturated water-soluble monomer comprises a monomer havingthe formula (VI):

wherein m is an integer from 0 to 10; A is a methylene group; R⁴ is ahydrogen atom, a phenyl group, or a benzyl group; R⁵ is a hydrogen atom,or a lower alkyl or carboxyl group; R⁶ is a hydrogen atom, a lower alkylgroup, —CH₂COOH, a phenyl group, a benzyl group, or a polymeric groupcomprising a unit derived from a sulfonic acid; and Z is COOH,COO(B)_(n)Y¹, or CON(R⁷)R⁸, wherein R⁷ and R⁸ is each independentlyhydrogen or (B)_(n)Y¹; B is a methylene group; n is an integer from 1 to10; and Y¹ is a hydroxyl group, primary amine, secondary amine, tertiaryamine, or quaternary ammonium salt.
 13. The copolymer of claim 1,wherein said at least one unsaturated water-soluble monomer comprises acarboxylic acid.
 14. The copolymer of claim 1, wherein said at least oneunsaturated water-soluble monomer is an acrylic acid.
 15. The copolymerof claim 1, wherein said copolymer is a random copolymer, a blockcopolymer, or a graft copolymer.
 16. A composition comprising anelectrolyte and a copolymer for modifying rheology, formed of monomerunits consisting essentially of: at least one first monomer unitcomprising a polyhedral oligomeric silsesquioxane having anethylenically unsaturated radical; at least one second monomer unitcomprising an unsaturated oligo-poly(dimethyl siloxane)(meth)acrylate;and a sufficient amount of at least one unsaturated water-solublemonomer, such that said copolymer is soluble in water.
 17. A method ofmodifying the rheology of an environment comprising an electrolyte, themethod comprising adding a copolymer for modifying rheology, formed ofmonomer units consisting essentially of: at least one first monomer unitcomprising a polyhedral oligomeric silsesquioxane having anethylenically unsaturated radical; at least one second monomer unitcomprising an unsaturated oligo-poly(dimethyl siloxane)(meth)acrylate;and a sufficient amount of at least one unsaturated water-solublemonomer, such that said copolymer is soluble in water, to theenvironment.
 18. The method of claim 17, wherein the environmentcomprises a solution and the copolymer is added to the solution.